I know someone that can't eat citrus foods or foods with high acidity so when it comes to pizza this means having it with no tomato based sauces. So far this means having ranch or an Alfredo-type sauce, or worse yet no sauce! Aside from these can anyone suggest any other alternatives we can try?

Sure, you can use any alternative you like, but it's no longer real pizza then!
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NoldorinSep 25 '10 at 21:56

1

@Noldorin - Pizza is not defined by having tomato sauce. Pizza Bianca for example specifically does NOT include tomatoes.
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AllisonJan 26 '11 at 17:52

@Allison: Originally, it only had tomato sauce, and no cheese. The Pizza Napolitan is the original form of pizza, and was made as such. I'm sure many other Italians can agree with me on this. Undoubtedly, Americans and other Non-Italians will bastardise the food at some point, but they're taking liberty in calling it 'pizza' then.
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NoldorinJan 26 '11 at 18:07

You may need to rethink your idea of pizza as something that needs tomato sauce, or sauce at all. Imagine it as an open sandwhich freshly baked. You can put tomato or any other juicy thing to contribute moist.

Avoiding tomato will allow you to add some flavours that tomato sauce usually masks. If you like the pineapple-ham combo, it tastes better without tomato, IMHO.

A few of my favourite pizzas:

Slightly fried salmon (fry the chunks until they don't look raw), goat cheese and mozzarella. Add some olives after baking.

Yes! Take 1 cup slice onion, 1/2 cup butternut squash, peeled and sliced very thin. Put onion and squash in a roasting pan, add some rosemary, salt and pepper, toss with 2 tablespoons olive oil, and bake for about 20 minutes at 400 F. Brush your crust with olive oil. Put squash mixture on top, sprinkle a bunch of parmesan or asiago cheese over, then bake at 450 for about 10 minutes. Not sure what crust you use...but this is truly delicious!

You don't need sauce at all. Infuse some olive oil with garlic and let it cool down. Use it as your base, you can perhaps integrate fresh thyme, oregano, basil, or sage with your oil infusion depending on what your toppings might be

Pizza does not need a sauce, but most Americans are accustomed to eating pizzas with sauce covered bases. There are a variety of sauces that could be used in lieu of tomato based sauces, some of them people would accept readily while others might take a leap of faith... Basically any sauce can be used on pizza as long as you pair it with toppings that work with them.

More "Traditional" sauces:

Alfredo or other cream-based sauces

Pestos (There are many variation of pesto, not just basil)

Romesco

Olive oil (plain or herb infused)

Roasted garlic puree

"Modern" sauces:

Caramelized onions (with or without a splash of Balsamic to brighten the flavor)

Balsamic reduction (cooking down Balsamic vinegar makes it less acidic)

Ranch or other salad dressings like Blue Cheese or Caesar

Moles or Green salsa for Tex Mex flavor combinations

BBQ (this may not apply for the OP because it can be tomato based and acidic)

When I make homemade pizza I use this no-tomato sauce. Please note, beets will discolor as you cook them so while the sauce itself is nice and red, once you bake the pizza it may be a bit browner. (You may want to remove the sauce from the heat before adding the beets and don't cook them for the additional 5 minutes, then allow it to finish cooking while baking in the oven on the pizza.) You can see a photo of the baked sauce here.